CVE-2025-39748bpf: Forget ranges when refining tnum after JSET

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Forget ranges when refining tnum after JSET Syzbot reported a kernel warning due to a range invariant violation on the following BPF program. 0: call bpf_get_netns_cookie 1: if r0 == 0 goto <exit> 2: if r0 & Oxffffffff goto <exit> The issue is on the path where we fall through both jumps. That path is unreachable at runtime: after insn 1, we know r0 != 0, but with the sign extension on the jset, we would only fallthrough insn 2 if r0 == 0. Unfortunately, is_branch_taken() isn't currently able to figure this out, so the verifier walks all branches. The verifier then refines the register bounds using the second condition and we end up with inconsistent bounds on this unreachable path: 1: if r0 == 0 goto <exit> r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff) 2: if r0 & 0xffffffff goto <exit> r0 before reg_bounds_sync: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0) r0 after reg_bounds_sync: u64=[0x1, 0] var_off=(0, 0) Improving the range refinement for JSET to cover all cases is tricky. We also don't expect many users to rely on JSET given LLVM doesn't generate those instructions. So instead of improving the range refinement for JSETs, Eduard suggested we forget the ranges whenever we're narrowing tnums after a JSET. This patch implements that approach.

Timeline

Scores

EPSS (exploitation in 30 days)

0.18% · top 92% of all CVEs (12 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Affected products

• Linux · Linux

  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < 22191359f8454b0be082c3b126f86bcbea0f1318
  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < c29dd8336236a4deb75596b52d2dd16ccc4a380d
  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < 591c788d16046edb0220800bf1819554af5853ce
  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < 0643aa2468192a4d81326e8e76543854870b1ee2
  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < f01e06930444cab289a8783017af9b64255bd103
  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < 2fd0c26bacd90ef26522bd3169000a4715bf151f
  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < 80a6b11862a7cfdf691e8f9faee89cfea219f098
  • affected 960ea056561a08e2b837b2f02d22c53226414a84 – < 6279846b9b2532e1b04559ef8bd0dec049f29383

• Linux · Linux

  • affected 5.0
  • unaffected < 5.0
  • unaffected 5.10.253 – ≤ 5.10.*
  • unaffected 5.15.203 – ≤ 5.15.*
  • unaffected 6.1.167 – ≤ 6.1.*
  • unaffected 6.6.130 – ≤ 6.6.*
  • unaffected 6.12.43 – ≤ 6.12.*
  • unaffected 6.15.11 – ≤ 6.15.*
  • unaffected 6.16.2 – ≤ 6.16.*
  • unaffected 6.17 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2025-28963 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2025-39748](https://cveledger.app/badge/CVE-2025-39748.svg)](https://cveledger.app/cve/CVE-2025-39748)

Record last updated 10 Nov 2026, 12:36 UTC.