Description
The Linux kernel 2.6.20 and 2.6.21 does not properly handle an invalid LDT segment selector in %cs (the xcs field) during ptrace single-step operations, which allows local users to cause a denial of service (NULL dereference and OOPS) via certain code that makes ptrace PTRACE_SETREGS and PTRACE_SINGLESTEP requests, related to the TRACE_IRQS_ON function, and possibly related to the arch_ptrace function.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 4.0 | fai-kernels | 1.17+etch.13etch3 | DSA-1378-2, DSA-1378-1 |
| Debian 4.0 | linux-2.6 | 2.6.18.dfsg.1-13etch3 | DSA-1378-2, DSA-1378-1 |
| Debian 4.0 | user-mode-linux | 2.6.18-1um-2etch.13etch3 | DSA-1378-2, DSA-1378-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 5 | kernel +9 | 2.6.18-8.1.15.el5 | RHSA-2007:0940 |
Advisories 3
- RHSA-2007:0940 Red Hat Security Advisory: kernel security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-1378-2 fai-kernels linux-2.6 user-mode-linux - several vulnerabilities Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-1378-1 fai-kernels linux-2.6 user-mode-linux - several vulnerabilities Debian Security (DSA / DLA) · Mar 9, 2026
References
- 25801 vdb-entry
- http://bugzilla.kernel.org/show_bug.cgi?id=8765
- http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commitdiff%3Bh=a10d9a71bafd3a283da240d2868e71346d2aef6f
- 37286 vdb-entry
- RHSA-2007:0940 vendor-advisory
- 29159 third-party-advisory
- http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commitdiff%3Bh=29eb51101c02df517ca64ec472d7501127ad1da8
- 27322 third-party-advisory
- http://wiki.rpath.com/wiki/Advisories:rPSA-2008-0094
- 26978 third-party-advisory
- 20080229 rPSA-2008-0094-1 kernel mailing-list
- https://issues.rpath.com/browse/RPL-2304
- USN-518-1 vendor-advisory
- 26955 third-party-advisory
- oval:org.mitre.oval:def:10394 vdb-entry signature
- https://bugzilla.redhat.com/show_bug.cgi?id=248324
- 26935 third-party-advisory
- DSA-1378 vendor-advisory