Linux: Double Free
CVE-2026-52993 is a critical-severity double free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions a438975a6dcdbd70865978c021650d1485586f0b, 4ee4deadaae7cb2e3d53af0fc889cf92a73413c0, d3556656c6daebf8def751c7e71d11dd0a180d24 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to a438975a6dcdbd70865978c021650d1485586f0b or 4ee4deadaae7cb2e3d53af0fc889cf92a73413c0 or d3556656c6daebf8def751c7e71d11dd0a180d24 or 0274f24485fc38032d4093e463dc3ff5c7a667c9, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.258 or 5.15.209 or 6.1.175 or 6.6.141, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, a438975a6dcdbd70865978c021650d1485586f0b; d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, 4ee4deadaae7cb2e3d53af0fc889cf92a73413c0; d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, d3556656c6daebf8def751c7e71d11dd0a180d24; d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, 0274f24485fc38032d4093e463dc3ff5c7a667c9; d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, 4d104882bc815d4ec666ace9155f5f52715879a6; d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, 1d5e589055880fae229e229e1929e087dbe08cf3; d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, 29940fff14110ca48c5ccc168d121665b51bb778; d618d09a68e4eed7a435beb2e355250f6f40664a up to, but not including, d293ca716e7d5dffdaecaf6b9b2f857a33dc3d3a; and 1 more ranges | a438975a6dcdbd70865978c021650d1485586f0b, 4ee4deadaae7cb2e3d53af0fc889cf92a73413c0, d3556656c6daebf8def751c7e71d11dd0a180d24, 0274f24485fc38032d4093e463dc3ff5c7a667c9, 4d104882bc815d4ec666ace9155f5f52715879a6, 1d5e589055880fae229e229e1929e087dbe08cf3 |
| Red Hat | Red Hat Enterprise Linux 10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 6 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 7 | Not specified in the record | Not stated |
| Linux | Linux Kernel | 4.15 up to, but not including, 5.10.258; 5.11 up to, but not including, 5.15.209; 5.16 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.91; 6.13 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.10 | 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA |
| CVSS 3.1 | 7.0 | High | CNA |
Official description
In the Linux kernel, the following vulnerability has been resolved: tipc: fix double-free in tipc_buf_append() tipc_msg_validate() can potentially reallocate the skb it is validating, freeing the old one. In tipc_buf_append(), it was being called with a pointer to a local variable which was a copy of the caller's skb pointer. If the skb was reallocated and validation subsequently failed, the error handling path would free the original skb pointer, which had already been freed, leading to double-free. Fix this by checking if head now points to a newly allocated reassembled skb. If it does, reassign *headbuf for later freeing operations.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Double Free
The product calls free() twice on the same memory address.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
- Use a static analysis tool to find double free instances.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/0274f24485fc38032d4093e463dc3ff5c7a667c9
- git.kernel.org/stable/c/1d5e589055880fae229e229e1929e087dbe08cf3
- git.kernel.org/stable/c/29940fff14110ca48c5ccc168d121665b51bb778
- git.kernel.org/stable/c/4d104882bc815d4ec666ace9155f5f52715879a6
- git.kernel.org/stable/c/4ee4deadaae7cb2e3d53af0fc889cf92a73413c0
- git.kernel.org/stable/c/a438975a6dcdbd70865978c021650d1485586f0b
- git.kernel.org/stable/c/d293ca716e7d5dffdaecaf6b9b2f857a33dc3d3a
- git.kernel.org/stable/c/d3556656c6daebf8def751c7e71d11dd0a180d24
Third-party and government advisories
- access.redhat.com/security/cve/CVE-2026-52993Third Party Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2492437Third Party Advisory
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52993.jsonThird Party Advisory
Other references
Recent Double Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
- 7.8 High severity
- 8.8 High severity
- 7.8 High severity
Spotted an error? Tell us.