Description
Use-after-free vulnerability in the fasync_helper function in fs/fcntl.c in the Linux kernel before 2.6.33-rc4-git1 allows local users to gain privileges via vectors that include enabling O_ASYNC (aka FASYNC or FIOASYNC) on a locked file, and then closing this file.
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.
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 5 | kernel +11 | 2.6.18-164.11.1.el5 | RHSA-2010:0046 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 5.3 EUS | kernel +11 | 2.6.18-128.14.1.el5 | RHSA-2010:0149 |
| Red Hat MRG 1 | kernel-rt +9 | 2.6.24.7-149.el5rt | RHSA-2010:0161 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Exploit-DB 1
- Linux Kernel < 2.6.28 - 'fasync_helper()' Local Privilege Escalation EDB-33523 · local · Dec 16, 2009 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 3
- RHSA-2010:0149 Red Hat Security Advisory: kernel security and bug fix update Red Hat Security Advisories (RHSA) · Jun 29, 2026
- RHSA-2010:0046 Red Hat Security Advisory: kernel security and bug fix update Red Hat Security Advisories (RHSA) · Jun 29, 2026
- RHSA-2010:0161 Red Hat Security Advisory: kernel-rt security and bug fix update Red Hat Security Advisories (RHSA) · Jun 28, 2026
References
- http://www.kernel.org/pub/linux/kernel/v2.6/snapshots/patch-2.6.33-rc4-git1.bz2
- oval:org.mitre.oval:def:9201 vdb-entry signature
- 37806 vdb-entry
- http://twitter.com/taviso/statuses/7744108017
- http://support.avaya.com/css/P8/documents/100073666
- http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=53281b6d34d44308372d16acb7fb5327609f68b6
- 20100114 Locked fasync file descriptors can be referenced after free in >= 2.6.28 mailing-list
- oval:org.mitre.oval:def:7054 vdb-entry signature
- https://bugzilla.redhat.com/show_bug.cgi?id=547906
- 39033 third-party-advisory
- http://lock.cmpxchg8b.com/5ebe2294ecd0e0f08eab7690d2a6ee69/create_elf_tables.c
- 38199 third-party-advisory
- RHSA-2010:0095 vendor-advisory
- RHSA-2010:0046 vendor-advisory
- SUSE-SA:2010:010 vendor-advisory
- RHSA-2010:0161 vendor-advisory