CVE-2021-47131net/tls: Fix use-after-free after the TLS device goes down and up
- 8.1HighCVSS base score
- 0.75%Exploitation in 30 daysEPSS · top 44% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: net/tls: Fix use-after-free after the TLS device goes down and up When a netdev with active TLS offload goes down, tls_device_down is called to stop the offload and tear down the TLS context. However, the socket stays alive, and it still points to the TLS context, which is now deallocated. If a netdev goes up, while the connection is still active, and the data flow resumes after a number of TCP retransmissions, it will lead to a use-after-free of the TLS context. This commit addresses this bug by keeping the context alive until its normal destruction, and implements the necessary fallbacks, so that the connection can resume in software (non-offloaded) kTLS mode. On the TX side tls_sw_fallback is used to encrypt all packets. The RX side already has all the necessary fallbacks, because receiving non-decrypted packets is supported. The thing needed on the RX side is to block resync requests, which are normally produced after receiving non-decrypted packets. The necessary synchronization is implemented for a graceful teardown: first the fallbacks are deployed, then the driver resources are released (it used to be possible to have a tls_dev_resync after tls_dev_del). A new flag called TLS_RX_DEV_DEGRADED is added to indicate the fallback mode. It's used to skip the RX resync logic completely, as it becomes useless, and some objects may be released (for example, resync_async, which is allocated and freed by the driver).
Timeline
ID reserved
By Linux
- 11 days later
· 11 days later
Published
- 2 years later
· 2 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High8.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Modified | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.75% · top 44% of all CVEs (13 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: High 8.1.
Affected products
- affected e8f69799810c32dd40c6724d829eccc70baad07f – < f1d4184f128dede82a59a841658ed40d4e6d3aa2
- affected e8f69799810c32dd40c6724d829eccc70baad07f – < 0f1e6fe66977a864fe850522316f713d7b926fd9
- affected e8f69799810c32dd40c6724d829eccc70baad07f – < c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4
- affected 4.18
- unaffected < 4.18
- unaffected 5.10.43 – ≤ 5.10.*
- unaffected 5.12.10 – ≤ 5.12.*
- unaffected 5.13 – ≤ *
References
References3
- https://git.kernel.org/stable/c/f1d4184f128dede82a59a841658ed40d4e6d3aa2 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/0f1e6fe66977a864fe850522316f713d7b926fd9 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4 (opens in a new tab)x_transferred
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-2021-33779 (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
[](https://cveledger.app/cve/CVE-2021-47131)Record last updated .