CyberSecBulletin
CVE-2024-52811NVD status: Deferred

ngtcp2: Always-Incorrect Control Flow Implementation

Published Updated By the CyberSecBulletin desk

CVE-2024-52811 is a high-severity always-incorrect control flow implementation vulnerability in ngtcp2, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected ngtcp2 versions: = 1.9.0; 1.9.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.84% chance of exploitation within 30 days, higher than 58% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of ngtcp2 you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Ngtcp2ngtcp2= 1.9.0; 1.9.0Not stated

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
NoneNo data is disclosed.
Integrity
LowLimited modification of data is possible.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H. Scored by CNA (github.com).

Official description

The ngtcp2 project is an effort to implement IETF QUIC protocol in C. In affected versions acks are not validated before being written to the qlog leading to a buffer overflow. In `ngtcp2_conn::conn_recv_pkt` for an ACK, there was new logic that got added to skip `conn_recv_ack` if an ack has already been processed in the payload. However, this causes us to also skip `ngtcp2_pkt_validate_ack`. The ack which was skipped still got written to qlog. The bug occurs in `ngtcp2_qlog::write_ack_frame`. It is now possible to reach this code with an invalid ack, suppose `largest_ack=0` and `first_ack_range=15`. Subtracting `largest_ack - first_ack_range` will lead to an integer underflow which is 20 chars long. However, the ngtcp2 qlog code assumes the number written is a signed integer and only accounts for 19 characters of overhead (see `NGTCP2_QLOG_ACK_FRAME_RANGE_OVERHEAD`). Therefore, we overwrite the buffer causing a heap overflow. This is high priority and could potentially impact many users if they enable qlog. qlog is disabled by default. Due to its overhead, it is most likely used for debugging purpose, but the actual use is unknown. ngtcp2 v1.9.1 fixes the bug and users are advised to upgrade. Users unable to upgrade should not turn on qlog.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Always-Incorrect Control Flow Implementation

The code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated.

More Always-Incorrect Control Flow Implementation vulnerabilities (CWE-670)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in ngtcp2

All ngtcp2 vulnerabilities

Recent Always-Incorrect Control Flow Implementation vulnerabilities

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