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CVE-2026-43009high7.8

bpf: Fix incorrect pruning due to atomic fetch precision tracking

Impact

In the Linux kernel, the following vulnerability has been resolved:

Source excerpt · Linux

Affected packages

This source has no supported package-version data for matching. You can read the advisory here, but this record alone cannot power a dependency check.

Affected products

Vendor version evidence. Product records are separate from automatic dependency matching.

Linux · Linux

Linux

6 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

5ca419f2864a2c60940dcf4bbaeb69546200e36f → before 06999c8a2c52b13977771ab093b8e179821b532d

git versions

5ca419f2864a2c60940dcf4bbaeb69546200e36f → before 1aac6b271e0a80b91c2f6a8f75ab0c0b1fc8ffe8

git versions

5ca419f2864a2c60940dcf4bbaeb69546200e36f → before 7c72e5f3741d1c5cc53439137162f0e09254e6e9

git versions

5ca419f2864a2c60940dcf4bbaeb69546200e36f → before ea150ffa9fc9f78c5cf22e1f7b06b6d016b1017c

git versions

5ca419f2864a2c60940dcf4bbaeb69546200e36f → before 7ffbe45b1d227e24659998a91cfd4c27af457e71

git versions

5ca419f2864a2c60940dcf4bbaeb69546200e36f → before 179ee84a89114b854ac2dd1d293633a7f6c8dac1

git versions

unaffected

unknown

Other versions: unaffected

Linux · Linux

Linux

8 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

5.12

unaffected

0 → before 5.12

semver versions

6.1.191 → through 6.1.*

semver versions

6.6.160 → through 6.6.*

semver versions

6.12.114 → through 6.12.*

semver versions

6.18.50 → through 6.18.*

semver versions

6.19.12 → through 6.19.*

semver versions

7.0 → through *

original_commit_for_fix versions

unknown

Other versions: affected

Original source description

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix incorrect pruning due to atomic fetch precision tracking

When backtrack_insn encounters a BPF_STX instruction with BPF_ATOMIC and BPF_FETCH, the src register (or r0 for BPF_CMPXCHG) also acts as a destination, thus receiving the old value from the memory location.

The current backtracking logic does not account for this. It treats atomic fetch operations the same as regular stores where the src register is only an input. This leads the backtrack_insn to fail to propagate precision to the stack location, which is then not marked as precise!

Later, the verifier's path pruning can incorrectly consider two states equivalent when they differ in terms of stack state. Meaning, two branches can be treated as equivalent and thus get pruned when they should not be seen as such.

Fix it as follows: Extend the BPF_LDX handling in backtrack_insn to also cover atomic fetch operations via is_atomic_fetch_insn() helper. When the fetch dst register is being tracked for precision, clear it, and propagate precision over to the stack slot. For non-stack memory, the precision walk stops at the atomic instruction, same as regular BPF_LDX. This covers all fetch variants.

Before:

0: (b7) r1 = 8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5: (0f) r3 += r2 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10 mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0: regs=r2 stack= before 2: (b7) r2 = 0 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit

After:

0: (b7) r1 = 8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5: (0f) r3 += r2 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10 mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0 mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1 mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit

Inside the record

Evidence available

Package identity · not supplied
Version evidence
Remediation guidance · not supplied
Weakness classification
Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-43009

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-682 ↗

CWE-682 Incorrect Calculation

CISA-ADP

Related →

Environment requirements

These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.

Linux · platform conditions

Any condition may hold

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.12

Before: 6.1.191

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.12

Before: 6.6.160

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.12

Before: 6.12.114

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.12

Before: 6.18.50

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.12

Before: 6.19.12

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.12

Before: 7.0

Original applicability statements
[
  {
    "nodes": [
      {
        "operator": "OR",
        "negate": false,
        "cpeMatch": [
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "5.12",
            "versionEndExcluding": "6.1.191"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "5.12",
            "versionEndExcluding": "6.6.160"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "5.12",
            "versionEndExcluding": "6.12.114"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "5.12",
            "versionEndExcluding": "6.18.50"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "5.12",
            "versionEndExcluding": "6.19.12"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "5.12",
            "versionEndExcluding": "7.0"
          }
        ]
      }
    ]
  }
]
Contributing organizations · 2
Linux

Assigning organization

2026-10-30
CISA-ADP

Additional data publisher

2026-10-19

What changed

Follow changes
No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.

References

6 sources
git.kernel.org/stable/c/06999c8a2c52b13977771ab093b8e179821b532d
Source referenceLinux
git.kernel.org/stable/c/1aac6b271e0a80b91c2f6a8f75ab0c0b1fc8ffe8
Source referenceLinux
git.kernel.org/stable/c/7c72e5f3741d1c5cc53439137162f0e09254e6e9
Source referenceLinux
git.kernel.org/stable/c/ea150ffa9fc9f78c5cf22e1f7b06b6d016b1017c
Source referenceLinux
git.kernel.org/stable/c/7ffbe45b1d227e24659998a91cfd4c27af457e71
Source referenceLinux
git.kernel.org/stable/c/179ee84a89114b854ac2dd1d293633a7f6c8dac1
Source referenceLinux