CVE-2021-26691

In Apache HTTP Server versions 2.4.0 to 2.4.46 a specially crafted SessionHeader sent by an origin server could cause a heap overflow

In Apache HTTP Server versions 2.4.0 to 2.4.46 a specially crafted SessionHeader sent by an origin server could cause a heap overflow

Apache HTTP Server is a powerful and flexible HTTP/1.1 compliant web server.

Security Fix(es):

In Apache HTTP Server versions 2.4.0 to 2.4.46 a specially crafted SessionHeader sent by an origin server could cause a heap overflow(CVE-2021-26691)

Apache HTTP Server versions 2.4.41 to 2.4.46 mod_proxy_http can be made to crash (NULL pointer dereference) with specially crafted requests using both Content-Length and Transfer-Encoding headers, leading to a Denial of Service(CVE-2020-13950)

Apache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted Digest nonce can cause a stack overflow in mod_auth_digest. There is no report of this overflow being exploitable, nor the Apache HTTP Server team could create one, though some particular compiler and/or compilation option might make it possible, with limited consequences anyway due to the size (a single byte) and the value (zero byte) of the overflow(CVE-2020-35452)

Apache HTTP Server versions 2.4.39 to 2.4.46 Unexpected matching behavior with MergeSlashes OFF(CVE-2021-30641)

The httpd packages provide the Apache HTTP Server, a powerful, efficient, and extensible web server.

Security Fix(es):

• httpd: mod_proxy: SSRF via a crafted request uri-path containing "unix:" (CVE-2021-40438)

• httpd: mod_session: Heap overflow via a crafted SessionHeader value (CVE-2021-26691)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

In Apache HTTP Server versions 2.4.0 to 2.4.46 a specially crafted SessionHeader sent by an origin server could cause a heap overflow

The httpd packages provide the Apache HTTP Server, a powerful, efficient, and extensible web server.

Security Fix(es):

• httpd: mod_proxy: SSRF via a crafted request uri-path containing "unix:" (CVE-2021-40438)

• httpd: mod_session: Heap overflow via a crafted SessionHeader value (CVE-2021-26691)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The httpd packages provide the Apache HTTP Server, a powerful, efficient, and extensible web server.

Security Fix(es):

• httpd: Regression of CVE-2021-40438 and CVE-2021-26691 fixes in AlmaLinux (CVE-2021-20325)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

In Apache HTTP Server versions 2.4.0 to 2.4.46 a specially crafted SessionHeader sent by an origin server could cause a heap overflow

• SECURITY UPDATE: Unexpected URL matching with 'MergeSlashes OFF'
  • debian/patches/CVE-2021-30641.patch: legacy default slash-matching behavior with 'MergeSlashes OFF'.
  • CVE-2021-30641
• SECURITY UPDATE: heap overflow in mod_session
  • debian/patches/CVE-2021-26691.patch: A specially crafted SessionHeader sent by an origin server could cause a heap overflow.
  • CVE-2021-26691
• SECURITY UPDATE: NULL pointer dereference in mod_session
  • debian/patches/CVE-2021-26690.patch: A specially crafted Cookie header handled by mod_session can cause a NULL pointer dereference and crash, leading to a possible Denial Of Service.
  • CVE-2021-26690
• SECURITY UPDATE: mod_auth_digest possible stack overflow by one nul byte
  • debian/patches/CVE-2020-35452.patch: A specially crafted Digest nonce can cause a stack overflow in mod_auth_digest.
  • CVE-2020-35452

mod_proxy_wstunnel tunneling of non Upgraded connections: Apache HTTP Server versions 2.4.6 to 2.4.46 mod_proxy_wstunnel configured on an URL that is not necessarily Upgraded by the origin server was tunneling the whole connection regardless, thus allowing for subsequent requests on the same connection to pass through with no HTTP validation, authentication or authorization possibly configured. (CVE-2019-17567).

mod_proxy_http NULL pointer dereference: Apache HTTP Server versions 2.4.41 to 2.4.46 mod_proxy_http can be made to crash (NULL pointer dereference) with specially crafted requests using both Content-Length and Transfer-Encoding headers, leading to a Denial of Service (CVE-2020-13950).

mod_auth_digest possible stack overflow by one nul byte: Apache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted Digest nonce can cause a stack overflow in mod_auth_digest. There is no report of this overflow being exploitable, nor the Apache HTTP Server team could create one, though some particular compiler and/or compilation option might make it possible, with limited consequences anyway due to the size (a single byte) and the value (zero byte) of the overflow (CVE-2020-35452).

mod_session NULL pointer dereference: Apache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted Cookie header handled by mod_session can cause a NULL pointer dereference and crash, leading to a possible Denial Of Service (CVE-2021-26690).

mod_session response handling heap overflow: Apache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted SessionHeader sent by an origin server could cause a heap overflow (CVE-2021-26691).

Unexpected URL matching with 'MergeSlashes OFF': Apache HTTP Server versions 2.4.39 to 2.4.46 Unexpected matching behavior with 'MergeSlashes OFF'(CVE-2021-30641).

NULL pointer dereference on specially crafted HTTP/2 request: Apache HTTP Server protocol handler for the HTTP/2 protocol checks received request headers against the size limitations as configured for the server and used for the HTTP/1 protocol as well. On violation of these restrictions and HTTP response is sent to the client with a status code indicating why the request was rejected. This rejection response was not fully initialised in the HTTP/2 protocol handler if the offending header was the very first one received or appeared in a footer. This led to a NULL pointer dereference on initialised memory, crashing reliably the child process. Since such a triggering HTTP/2 request is easy to craft and submit, this can be exploited to DoS the server. This issue affected mod_http2 1.15.17 and Apache HTTP Server version 2.4.47 only. Apache HTTP Server 2.4.47 was never released. (CVE-2021-31618).

This update for apache2 fixes the following issues:

• fixed CVE-2021-30641 [bsc#1187174]: MergeSlashes regression
• fixed CVE-2021-31618 [bsc#1186924]: NULL pointer dereference on specially crafted HTTP/2 request
• fixed CVE-2020-13950 [bsc#1187040]: mod_proxy NULL pointer dereference
• fixed CVE-2020-35452 [bsc#1186922]: Single zero byte stack overflow in mod_auth_digest
• fixed CVE-2021-26690 [bsc#1186923]: mod_session NULL pointer dereference in parser
• fixed CVE-2021-26691 [bsc#1187017]: Heap overflow in mod_session

This update for apache2 fixes the following issues:

• fixed CVE-2021-30641 [bsc#1187174]: MergeSlashes regression
• fixed CVE-2021-31618 [bsc#1186924]: NULL pointer dereference on specially crafted HTTP/2 request
• fixed CVE-2020-13950 [bsc#1187040]: mod_proxy NULL pointer dereference
• fixed CVE-2020-35452 [bsc#1186922]: Single zero byte stack overflow in mod_auth_digest
• fixed CVE-2021-26690 [bsc#1186923]: mod_session NULL pointer dereference in parser
• fixed CVE-2021-26691 [bsc#1187017]: Heap overflow in mod_session

This update for apache2 fixes the following issues:

• CVE-2021-30641: Fixed MergeSlashes regression (bsc#1187174)
• CVE-2021-31618: Fixed NULL pointer dereference on specially crafted HTTP/2 request (bsc#1186924)
• CVE-2020-35452: Fixed Single zero byte stack overflow in mod_auth_digest (bsc#1186922)
• CVE-2021-26690: Fixed mod_session NULL pointer dereference in parser (bsc#1186923)
• CVE-2021-26691: Fixed Heap overflow in mod_session (bsc#1187017)
• Fixed potential content spoofing with default error pages (bsc#1182703)
• Fixed for an issue when 'gensslcert' does not set CA:True. (bsc#1180530)

This update for apache2 fixes the following issues:

• fixed CVE-2021-30641 [bsc#1187174]: MergeSlashes regression
• fixed CVE-2021-31618 [bsc#1186924]: NULL pointer dereference on specially crafted HTTP/2 request
• fixed CVE-2020-35452 [bsc#1186922]: Single zero byte stack overflow in mod_auth_digest
• fixed CVE-2021-26690 [bsc#1186923]: mod_session NULL pointer dereference in parser
• fixed CVE-2021-26691 [bsc#1187017]: Heap overflow in mod_session

This update for apache2 fixes the following issues:

• fixed CVE-2021-30641 [bsc#1187174]: MergeSlashes regression
• fixed CVE-2021-31618 [bsc#1186924]: NULL pointer dereference on specially crafted HTTP/2 request
• fixed CVE-2020-13950 [bsc#1187040]: mod_proxy NULL pointer dereference
• fixed CVE-2020-35452 [bsc#1186922]: Single zero byte stack overflow in mod_auth_digest
• fixed CVE-2021-26690 [bsc#1186923]: mod_session NULL pointer dereference in parser
• fixed CVE-2021-26691 [bsc#1187017]: Heap overflow in mod_session

Marc Stern discovered that the Apache mod_proxy_http module incorrectly handled certain requests. A remote attacker could possibly use this issue to cause Apache to crash, resulting in a denial of service. This issue only affected Ubuntu 20.04 LTS, Ubuntu 20.10, and Ubuntu 21.04. (CVE-2020-13950)

Antonio Morales discovered that the Apache mod_auth_digest module incorrectly handled certain Digest nonces. A remote attacker could possibly use this issue to cause Apache to crash, resulting in a denial of service. (CVE-2020-35452)

Antonio Morales discovered that the Apache mod_session module incorrectly handled certain Cookie headers. A remote attacker could possibly use this issue to cause Apache to crash, resulting in a denial of service. (CVE-2021-26690)

Christophe Jaillet discovered that the Apache mod_session module incorrectly handled certain SessionHeader values. A remote attacker could use this issue to cause Apache to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2021-26691)

Christoph Anton Mitterer discovered that the new MergeSlashes configuration option resulted in unexpected behaviour in certain situations. (CVE-2021-30641)

USN-4994-1 fixed several vulnerabilities in Apache. This update provides the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.

Original advisory details:

Antonio Morales discovered that the Apache mod_auth_digest module incorrectly handled certain Digest nonces. A remote attacker could possibly use this issue to cause Apache to crash, resulting in a denial of service. (CVE-2020-35452)

Antonio Morales discovered that the Apache mod_session module incorrectly handled certain Cookie headers. A remote attacker could possibly use this issue to cause Apache to crash, resulting in a denial of service. (CVE-2021-26690)

Christophe Jaillet discovered that the Apache mod_session module incorrectly handled certain SessionHeader values. A remote attacker could use this issue to cause Apache to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2021-26691)

Christoph Anton Mitterer discovered that the new MergeSlashes configuration option resulted in unexpected behaviour in certain situations. (CVE-2021-30641)