# CVE-2026-31518: esp: fix skb leak with espintcp and async crypto

Status: published. Published: 2026-04-22. Updated: 2026-11-05.

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

esp: fix skb leak with espintcp and async crypto

When the TX queue for espintcp is full, esp_output_tail_tcp will
return an error and not free the skb, because with synchronous crypto,
the common xfrm output code will drop the packet for us.

With async crypto (esp_output_done), we need to drop the skb when
esp_output_tail_tcp returns an error.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < aca3ad0c262f54a5b5c95dda80a48365997d1224 (affected, git); ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < 41aafca57de4a4c026701622bd4648f112a9edcd (affected, git); ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < 4820847e036ff1035b01b69ad68dfc17e7028fe9 (affected, git); ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < 6a3ec6efbc4f90e0ccb2e71574f07351f19996f4 (affected, git); ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < df6f995358dc1f3c42484f5cfe241d7bd3e1cd15 (affected, git); ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < 88d386243ed374ac969dabd3bbc1409a31d81818 (affected, git); ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < 6aa9841d917532d0f2d932d1ff2f3a94305aaf47 (affected, git); ≥ e27cca96cd68fa2c6814c90f9a1cfd36bb68c593; < 0c0eef8ccd2413b0a10eb6bbd3442333b1e64dd2 (affected, git). Source: CNA: Linux
- Linux / Linux: 5.6 (affected); ≥ 0; < 5.6 (unaffected, semver); ≥ 5.10.253; ≤ 5.10.* (unaffected, semver); ≥ 5.15.203; ≤ 5.15.* (unaffected, semver); ≥ 6.1.168; ≤ 6.1.* (unaffected, semver); ≥ 6.6.131; ≤ 6.6.* (unaffected, semver); ≥ 6.12.80; ≤ 6.12.* (unaffected, semver); ≥ 6.18.21; ≤ 6.18.* (unaffected, semver); ≥ 6.19.11; ≤ 6.19.* (unaffected, semver); ≥ 7.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP: ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP: ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.5; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP: ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.13% as of 2026-11-05; percentile 2.54%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/aca3ad0c262f54a5b5c95dda80a48365997d1224 (CNA: Linux)

- https://git.kernel.org/stable/c/41aafca57de4a4c026701622bd4648f112a9edcd (CNA: Linux)

- https://git.kernel.org/stable/c/4820847e036ff1035b01b69ad68dfc17e7028fe9 (CNA: Linux)

- https://git.kernel.org/stable/c/6a3ec6efbc4f90e0ccb2e71574f07351f19996f4 (CNA: Linux)

- https://git.kernel.org/stable/c/df6f995358dc1f3c42484f5cfe241d7bd3e1cd15 (CNA: Linux)

- https://git.kernel.org/stable/c/88d386243ed374ac969dabd3bbc1409a31d81818 (CNA: Linux)

- https://git.kernel.org/stable/c/6aa9841d917532d0f2d932d1ff2f3a94305aaf47 (CNA: Linux)

- https://git.kernel.org/stable/c/0c0eef8ccd2413b0a10eb6bbd3442333b1e64dd2 (CNA: Linux)

- https://cert-portal.siemens.com/productcert/html/ssa-082556.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-019113.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-31518; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-31518; retrieved 2026-11-05; source updated Not reported

Revision: fee989093d06c3db6617d842cdd389b38dcacc82243e14acddc39eaee30f4a4d

Canonical: https://y2.dev/cve/CVE-2026-31518

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