high CVSS 7.8 EPSS <0.1%

CVE-2024-26800·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: tls: fix use-after-free on failed backlog decryption When the decrypt request goes to the backlog and crypto_aead_decrypt returns -EBUSY, tls_do_decryption will wait until all async decryptions have completed. If one of them fails, tls_do_decryption will return -EBADMSG and tls_decrypt_sg jumps to the error path, releasing all the pages. But the pages have been passed to the async callback, and have already been released by tls_decrypt_done. The only true async case is when crypto_aead_decrypt returns -EINPROGRESS. With -EBUSY, we already waited so we can tell tls_sw_recvmsg that the data is available for immediate copy, but we need to notify tls_decrypt_sg (via the new ->async_done flag) that the memory has already been released.

Severity
high
Software
Kernel
Fixed in
6.7.9
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 6% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2024-26800 scores 7.8 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 6.7.6

Until: 6.7.9

Fixed in: 6.7.9

How to fix this CVE

Update your Linux kernel to version 6.7.9 or later to resolve this use-after-free vulnerability affecting TLS backlog decryption. This patch corrects improper memory release handling when async crypto operations return -EBUSY, preventing kernel memory corruption. Systems running affected kernel versions 6.7.6 through 6.7.8 should prioritize this update and reboot to activate the patched kernel.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Run `uname -r` to display the currently running kernel version and compare against the vulnerable range 6.7.6-6.7.8
  2. Step 2: Execute `cat /proc/version` to confirm kernel build details and verify if TLS module (CONFIG_TLS) is enabled in the running kernel
  3. Step 3: Search kernel logs with `sudo dmesg | grep -i 'tls\|crypto\|ebadmsg\|use.*after.*free'` for signs of decryption failures or memory corruption
  4. Step 4: After applying the update, verify the new kernel version with `uname -r` and confirm it shows 6.7.9 or later, then review `dmesg` for clean TLS operation without memory errors

FAQ

What is CVE-2024-26800?

CVE-2024-26800 is a use-after-free vulnerability in the Linux kernel's TLS subsystem where memory pages are incorrectly released twice when backlog crypto decryption operations fail, potentially allowing memory corruption.

Is CVE-2024-26800 being actively exploited?

No, this vulnerability is not currently being exploited in the wild according to CISA KEV data, and no public exploits have been released.

What versions of Kernel are affected by CVE-2024-26800?

Linux kernel versions 6.7.6 through 6.7.8 are vulnerable; version 6.7.9 and later contain the fix.

How do I check if my server is vulnerable to CVE-2024-26800?

Run `uname -r` and check if the output falls within 6.7.6-6.7.8 range; if so, your system is vulnerable and requires immediate kernel update.

Does Defensia detect CVE-2024-26800?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2024-26800 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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References

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