CVE-2026-4371
Out of bounds read in IMAP parsing
CVE-2026-4371 is fixed in 134 products on 2 platforms, first by Mozilla Thunderbird (af) 149.0, released March 24, 2026. It is not reported as exploited. Patch Radar priority: High.
HighFixed on 2 platforms
CVSS
8.2
Important
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0037
30th percentile
A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Windows apps | |||
| Mozilla Thunderbird (af) | 149.0 | Mozilla Thunderbird (af) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ar) | 149.0 | Mozilla Thunderbird (ar) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ast) | 149.0 | Mozilla Thunderbird (ast) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (be) | 149.0 | Mozilla Thunderbird (be) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (bg) | 149.0 | Mozilla Thunderbird (bg) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (br) | 149.0 | Mozilla Thunderbird (br) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ca) | 149.0 | Mozilla Thunderbird (ca) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (cak) | 149.0 | Mozilla Thunderbird (cak) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (cs) | 149.0 | Mozilla Thunderbird (cs) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (cy) | 149.0 | Mozilla Thunderbird (cy) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (da) | 149.0 | Mozilla Thunderbird (da) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (de) | 149.0 | Mozilla Thunderbird (de) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (dsb) | 149.0 | Mozilla Thunderbird (dsb) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (el) | 149.0 | Mozilla Thunderbird (el) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (en-CA) | 149.0 | Mozilla Thunderbird (en-CA) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (en-GB) | 149.0 | Mozilla Thunderbird (en-GB) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (en-US) | 149.0 | Mozilla Thunderbird (en-US) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (es-AR) | 149.0 | Mozilla Thunderbird (es-AR) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (es-ES) | 149.0 | Mozilla Thunderbird (es-ES) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (es-MX) | 149.0 | Mozilla Thunderbird (es-MX) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (et) | 149.0 | Mozilla Thunderbird (et) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (eu) | 149.0 | Mozilla Thunderbird (eu) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (fi) | 149.0 | Mozilla Thunderbird (fi) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (fr) | 149.0 | Mozilla Thunderbird (fr) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (fy-NL) | 149.0 | Mozilla Thunderbird (fy-NL) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ga-IE) | 149.0 | Mozilla Thunderbird (ga-IE) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (gd) | 149.0 | Mozilla Thunderbird (gd) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (gl) | 149.0 | Mozilla Thunderbird (gl) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (he) | 149.0 | Mozilla Thunderbird (he) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (hr) | 149.0 | Mozilla Thunderbird (hr) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (hsb) | 149.0 | Mozilla Thunderbird (hsb) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (hu) | 149.0 | Mozilla Thunderbird (hu) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (hy-AM) | 149.0 | Mozilla Thunderbird (hy-AM) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (id) | 149.0 | Mozilla Thunderbird (id) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (is) | 149.0 | Mozilla Thunderbird (is) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (it) | 149.0 | Mozilla Thunderbird (it) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ja) | 149.0 | Mozilla Thunderbird (ja) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ka) | 149.0 | Mozilla Thunderbird (ka) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (kab) | 149.0 | Mozilla Thunderbird (kab) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (kk) | 149.0 | Mozilla Thunderbird (kk) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ko) | 149.0 | Mozilla Thunderbird (ko) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (lt) | 149.0 | Mozilla Thunderbird (lt) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (lv) | 149.0 | Mozilla Thunderbird (lv) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ms) | 149.0 | Mozilla Thunderbird (ms) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (nb-NO) | 149.0 | Mozilla Thunderbird (nb-NO) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (nl) | 149.0 | Mozilla Thunderbird (nl) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (nn-NO) | 149.0 | Mozilla Thunderbird (nn-NO) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (pa-IN) | 149.0 | Mozilla Thunderbird (pa-IN) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (pl) | 149.0 | Mozilla Thunderbird (pl) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (pt-BR) | 149.0 | Mozilla Thunderbird (pt-BR) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (pt-PT) | 149.0 | Mozilla Thunderbird (pt-PT) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (rm) | 149.0 | Mozilla Thunderbird (rm) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ro) | 149.0 | Mozilla Thunderbird (ro) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (ru) | 149.0 | Mozilla Thunderbird (ru) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (sk) | 149.0 | Mozilla Thunderbird (sk) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (sl) | 149.0 | Mozilla Thunderbird (sl) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (sq) | 149.0 | Mozilla Thunderbird (sq) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (sr) | 149.0 | Mozilla Thunderbird (sr) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (sv-SE) | 149.0 | Mozilla Thunderbird (sv-SE) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (th) | 149.0 | Mozilla Thunderbird (th) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (tr) | 149.0 | Mozilla Thunderbird (tr) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (uk) | 149.0 | Mozilla Thunderbird (uk) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (uz) | 149.0 | Mozilla Thunderbird (uz) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (vi) | 149.0 | Mozilla Thunderbird (vi) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (zh-CN) | 149.0 | Mozilla Thunderbird (zh-CN) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird (zh-TW) | 149.0 | Mozilla Thunderbird (zh-TW) 149.0 | Mar 24, 2026 |
| Mozilla Thunderbird ESR (af) | 153.0.1 | Mozilla Thunderbird ESR (af) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ar) | 153.0.1 | Mozilla Thunderbird ESR (ar) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ast) | 153.0.1 | Mozilla Thunderbird ESR (ast) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (be) | 153.0.1 | Mozilla Thunderbird ESR (be) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (bg) | 153.0.1 | Mozilla Thunderbird ESR (bg) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (br) | 153.0.1 | Mozilla Thunderbird ESR (br) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ca) | 153.0.1 | Mozilla Thunderbird ESR (ca) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (cak) | 153.0.1 | Mozilla Thunderbird ESR (cak) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (cs) | 153.0.1 | Mozilla Thunderbird ESR (cs) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (cy) | 153.0.1 | Mozilla Thunderbird ESR (cy) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (da) | 153.0.1 | Mozilla Thunderbird ESR (da) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (de) | 153.0.1 | Mozilla Thunderbird ESR (de) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (dsb) | 153.0.1 | Mozilla Thunderbird ESR (dsb) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (el) | 153.0.1 | Mozilla Thunderbird ESR (el) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (en-CA) | 153.0.1 | Mozilla Thunderbird ESR (en-CA) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (en-GB) | 153.0.1 | Mozilla Thunderbird ESR (en-GB) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (en-US) | 153.0.1 | Mozilla Thunderbird ESR (en-US) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (es-AR) | 153.0.1 | Mozilla Thunderbird ESR (es-AR) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (es-ES) | 153.0.1 | Mozilla Thunderbird ESR (es-ES) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (es-MX) | 153.0.1 | Mozilla Thunderbird ESR (es-MX) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (et) | 153.0.1 | Mozilla Thunderbird ESR (et) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (eu) | 153.0.1 | Mozilla Thunderbird ESR (eu) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (fi) | 153.0.1 | Mozilla Thunderbird ESR (fi) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (fr) | 153.0.1 | Mozilla Thunderbird ESR (fr) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (fy-NL) | 153.0.1 | Mozilla Thunderbird ESR (fy-NL) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ga-IE) | 153.0.1 | Mozilla Thunderbird ESR (ga-IE) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (gd) | 153.0.1 | Mozilla Thunderbird ESR (gd) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (gl) | 153.0.1 | Mozilla Thunderbird ESR (gl) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (he) | 153.0.1 | Mozilla Thunderbird ESR (he) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (hr) | 153.0.1 | Mozilla Thunderbird ESR (hr) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (hsb) | 153.0.1 | Mozilla Thunderbird ESR (hsb) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (hu) | 153.0.1 | Mozilla Thunderbird ESR (hu) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (hy-AM) | 153.0.1 | Mozilla Thunderbird ESR (hy-AM) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (id) | 153.0.1 | Mozilla Thunderbird ESR (id) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (is) | 153.0.1 | Mozilla Thunderbird ESR (is) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (it) | 153.0.1 | Mozilla Thunderbird ESR (it) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ja) | 153.0.1 | Mozilla Thunderbird ESR (ja) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ka) | 153.0.1 | Mozilla Thunderbird ESR (ka) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (kab) | 153.0.1 | Mozilla Thunderbird ESR (kab) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (kk) | 153.0.1 | Mozilla Thunderbird ESR (kk) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ko) | 153.0.1 | Mozilla Thunderbird ESR (ko) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (lt) | 153.0.1 | Mozilla Thunderbird ESR (lt) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (lv) | 153.0.1 | Mozilla Thunderbird ESR (lv) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ms) | 153.0.1 | Mozilla Thunderbird ESR (ms) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (nb-NO) | 153.0.1 | Mozilla Thunderbird ESR (nb-NO) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (nl) | 153.0.1 | Mozilla Thunderbird ESR (nl) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (nn-NO) | 153.0.1 | Mozilla Thunderbird ESR (nn-NO) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (pa-IN) | 153.0.1 | Mozilla Thunderbird ESR (pa-IN) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (pl) | 153.0.1 | Mozilla Thunderbird ESR (pl) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (pt-BR) | 153.0.1 | Mozilla Thunderbird ESR (pt-BR) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (pt-PT) | 153.0.1 | Mozilla Thunderbird ESR (pt-PT) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (rm) | 153.0.1 | Mozilla Thunderbird ESR (rm) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ro) | 153.0.1 | Mozilla Thunderbird ESR (ro) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (ru) | 153.0.1 | Mozilla Thunderbird ESR (ru) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (sk) | 153.0.1 | Mozilla Thunderbird ESR (sk) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (sl) | 153.0.1 | Mozilla Thunderbird ESR (sl) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (sq) | 153.0.1 | Mozilla Thunderbird ESR (sq) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (sr) | 153.0.1 | Mozilla Thunderbird ESR (sr) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (sv-SE) | 153.0.1 | Mozilla Thunderbird ESR (sv-SE) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (th) | 153.0.1 | Mozilla Thunderbird ESR (th) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (tr) | 153.0.1 | Mozilla Thunderbird ESR (tr) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (uk) | 153.0.1 | Mozilla Thunderbird ESR (uk) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (uz) | 153.0.1 | Mozilla Thunderbird ESR (uz) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (vi) | 153.0.1 | Mozilla Thunderbird ESR (vi) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (zh-CN) | 153.0.1 | Mozilla Thunderbird ESR (zh-CN) 153.0.1 | Jul 23, 2026 |
| Mozilla Thunderbird ESR (zh-TW) | 153.0.1 | Mozilla Thunderbird ESR (zh-TW) 153.0.1 | Jul 23, 2026 |
| Linux | |||
| MozillaThunderbird · opensuse-leap 15.6 | 140.9.0-150200.8.263.1 | SUSE-SU-2026:1163-1 | Apr 1, 2026 |
| thunderbird · Debian 12.15 (bookworm) | 1:140.9.0esr-1~deb12u1 | DEBIAN-CVE-2026-4371 | Mar 24, 2026 |
| thunderbird · Debian 13.5 (trixie) | 1:140.9.0esr-1~deb13u1 | DEBIAN-CVE-2026-4371 | Mar 24, 2026 |
| thunderbird · Debian 14 | 1:140.9.0esr-1 | DEBIAN-CVE-2026-4371 | Mar 24, 2026 |
| thunderbird · RHEL 10 | 140.9.0-1.el10_0 | RHSA-2026:8315 | Apr 15, 2026 |
| thunderbird · RHEL 8 | 0:140.9.0-1.el8_10 | RHSA-2026:6917 | Apr 15, 2026 |
| thunderbird · RHEL 9 | 0:140.9.0-1.el9_7 | RHSA-2026:6188 | Apr 15, 2026 |
| thunderbird · almalinux 10 | 140.9.0-1.el10_1.alma.1 | ALSA-2026:6342 | Apr 1, 2026 |
| thunderbird · almalinux 8 | 140.9.0-1.el8_10.alma.1 | ALSA-2026:6917 | Apr 7, 2026 |
| thunderbird · almalinux 9 | 140.9.0-1.el9_7.alma.1 | ALSA-2026:6188 | Mar 30, 2026 |
| thunderbird · ol 10 | 0:140.9.0-1.0.1.el10_1 | ELSA-2026-6342 | Apr 1, 2026 |
| thunderbird · ol 8 | 0:140.9.0-1.0.1.el8_10 | ELSA-2026-6917 | Apr 7, 2026 |
| thunderbird · ol 9 | 0:140.9.0-1.0.1.el9_7 | ELSA-2026-6188 | Mar 30, 2026 |
| thunderbird · rocky 10 | 0:140.9.0-1.el10_1 | RLSA-2026:6342 | Apr 9, 2026 |
| thunderbird · rocky 8 | 0:140.9.0-1.el8_10 | RLSA-2026:6917 | Apr 12, 2026 |
| thunderbird · rocky 9 | 0:140.9.0-1.el9_7 | RLSA-2026:6188 | Apr 7, 2026 |
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