CyberSecBulletin
CVE-2019-11043Exploited in the wildNVD status: Analyzed

PHP FastCGI Process Manager (FPM) Buffer Overflow

Published Updated By the CyberSecBulletin desk

CVE-2019-11043 is a critical-severity out-of-bounds write vulnerability in PHP, 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 7.1.33, 7.2.24, 7.3.11 as the first without the flaw, so updating PHP to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on March 25, 2022, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update PHP to 7.1.33 or 7.2.24 or 7.3.11, whichever matches your release line, or a later version.
  2. Update Tenable.sc to 5.19.0 or a later version.
  3. CISA's required action: Apply updates per vendor instructions.
  4. Read the advisory on bugs.php.net for workarounds and exact fixed builds.
  5. 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
PHPPHP7.1.x up to, but not including, 7.1.33; 7.2.x up to, but not including, 7.2.24; 7.3.x up to, but not including, 7.3.117.1.33, 7.2.24, 7.3.11
CanonicalUbuntu Linux12.04; 14.04; 16.04; 18.04; 19.04; 19.10Not stated
DebianDebian Linux9.0; 10.0Not stated
Fedora ProjectFedora29; 30; 31Not stated
TenableTenable.scbefore 5.19.05.19.0
Red HatSoftware Collections1.0Not stated
Red HatEnterprise Linux8.0Not stated
Red HatEnterprise Linux Desktop6.0; 7.0Not stated
Red HatEnterprise Linux EUS7.7; 8.1; 8.2; 8.4; 8.6; 8.8Not stated
Red HatEnterprise Linux EUS Compute Node7.7Not stated
Red HatEnterprise Linux For Arm 648.0_aarch64Not stated
Red HatEnterprise Linux For Arm 64 EUS8.1_aarch64; 8.2_aarch64; 8.4_aarch64; 8.6_aarch64; 8.8_aarch64Not stated
Red HatEnterprise Linux For IBM Z Systems6.0_s390x; 7.0_s390x; 8.0_s390xNot stated
Red HatEnterprise Linux For IBM Z Systems EUS7.7_s390x; 8.1_s390x; 8.2_s390x; 8.4_s390x; 8.6_s390x; 8.8_s390xNot stated
Red HatEnterprise Linux For Power Big Endian6.0_ppc64; 7.0_ppc64Not stated
Red HatEnterprise Linux For Power Big Endian EUS7.7_ppc64Not stated
Red HatEnterprise Linux For Power Little Endian7.0_ppc64le; 8.0_ppc64leNot stated
Red HatEnterprise Linux For Power Little Endian EUS7.7_ppc64le; 8.1_ppc64le; 8.2_ppc64le; 8.4_ppc64le; 8.6_ppc64le; 8.8_ppc64leNot stated
Red HatEnterprise Linux For Scientific Computing7.0Not stated
Red HatEnterprise Linux Server6.0; 7.0Not stated
Red HatEnterprise Linux Server AUS7.7; 8.2; 8.4; 8.6Not stated
Red HatEnterprise Linux Server TUS7.7; 8.2; 8.4; 8.6; 8.8Not stated
Red HatEnterprise Linux Workstation6.0; 7.0Not 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
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 NVD.

Scoring systemScoreSeverityScored by
CVSS 3.18.7HighCNA (php.net)
CVSS 3.19.8CriticalNVD
CVSS 2.07.5HighNVD

Official description

In PHP versions 7.1.x below 7.1.33, 7.2.x below 7.2.24 and 7.3.x below 7.3.11 in certain configurations of FPM setup it is possible to cause FPM module to write past allocated buffers into the space reserved for FCGI protocol data, thus opening the possibility of remote code execution.

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

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Advisories

Third-party and government advisories

Technical write-ups (may include proof of concept)

Other vulnerabilities in PHP

All PHP vulnerabilities

Recent Out-of-bounds Write vulnerabilities

Spotted an error? Tell us.