# CVE-2026-98040: linux: In the Linux kernel, the following vulnerability has been resolved:  bpf: Mark the zero register precise for a regist...

CVE-2026-98040 is fixed in linux on 1 platform by DEBIAN-CVE-2026-98040 (version 7.2.7-1), released October 2, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-98040
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 25, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  bpf: Mark the zero register precise for a register-form NULL check  check_cond_jmp_op() accepts "if rA <op> rB" as a NULL check for a nullable pointer rA when rB is a scalar known to be zero, lifts PTR_MAYBE_NULL from rA in the corresponding branch and does not mark rB precise. Consider the following program:    r0 = bpf_get_prandom_u32();   r6 = 1;                  /* the r6 == 0 path is explored first */   if (r0 == 0) goto 1f;   r6 = 0; 1:   r0 = bpf_map_lookup_elem(map, &0);  /* absent, NULL at runtime */   if (r0 == r6) goto 2f;   /* taken as a NULL check for r0       */   *(u8 *)(r0 + 0);         /* verifier: map value; runtime: zero */ 2:   return 0;  The r6 == 0 path is explored first and the dereference is accepted. The r6 == 1 path is pruned at the checkpoint recorded for (1), so the comparison is never verified with a non-zero r6. At runtime a failed lookup returns NULL, NULL != 1 takes the non-NULL edge and the program dereferences a pointer that is zero.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.7-1 | [DEBIAN-CVE-2026-98040](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98040.md) | Oct 2, 2026 |

---

Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.