CVE-2026-28810

Generation of Predictable Numbers or Identifiers vulnerability in Erlang/OTP kernel (inet_res, inet_db modules) allows DNS Cache Poisoning. The built-in DNS resolver (inet_res) uses a sequential, process-global 16-bit transaction ID for UDP queries and does not implement source port randomization. Response validation relies almost entirely on this ID, making DNS cache poisoning practical for an attacker who can observe one query or predict the next ID. This conflicts with RFC 5452 recommendations for mitigating forged DNS answers. inet_res is intended for use in trusted network environments and with trusted recursive resolvers. Earlier documentation did not clearly state this deployment assumption, which could lead users to deploy the resolver in environments where spoofed DNS responses are possible. This vulnerability is associated with program files lib/kernel/src/inet_db.erl and lib/kernel/src/inet_res.erl. This issue affects OTP from OTP 17.0 before OTP 28.4.2, OTP 27.3.4.10 and OTP 26.2.5.19, corresponding to kernel from 3.0 before 10.6.2, 10.2.7.4 and 9.2.4.11.

Generation of Predictable Numbers or Identifiers vulnerability in Erlang/OTP kernel (inet_res, inet_db modules) allows DNS Cache Poisoning.

The built-in DNS resolver (inet_res) uses a sequential, process-global 16-bit transaction ID for UDP queries and does not implement source port randomization. Response validation relies almost entirely on this ID, making DNS cache poisoning practical for an attacker who can observe one query or predict the next ID. This conflicts with RFC 5452 recommendations for mitigating forged DNS answers.

inet_res is intended for use in trusted network environments and with trusted recursive resolvers. Earlier documentation did not clearly state this deployment assumption, which could lead users to deploy the resolver in environments where spoofed DNS responses are possible.

This vulnerability is associated with program files lib/kernel/src/inet_db.erl and lib/kernel/src/inet_res.erl.

This issue affects OTP from OTP 17.0 before OTP 28.4.2, OTP 27.3.4.10 and OTP 26.2.5.19, corresponding to kernel from 3.0 before 10.6.2, 10.2.7.4 and 9.2.4.11.

These are all security issues fixed in the erlang27-27.1.3-2.1 package on the GA media of openSUSE Tumbleweed.

This update for erlang fixes the following issues:

Security issues fixed:

• CVE-2026-21620: improper isolation and compartmentalization can lead to TFTP relative path traversal and remote arbitrary reads/writes (bsc#1258663).
• CVE-2026-23941: improper handling of duplicate Content-Length headers in Erlang OTP can lead to HTTP request smuggling (bsc#1259687).
• CVE-2026-23942: improper limitation of a pathname to a restricted directory in the SFTP server can lead to path traversal (bsc#1259681).
• CVE-2026-23943: improper handling of highly compressed data in Erlang OTP ssh can lead to denial of service (bsc#1259682).
• CVE-2026-28808: incorrect authorization can lead to unauthenticated access to protected CGI scripts (bsc#1261728).
• CVE-2026-28810: predictable DNS transaction IDs can lead to DNS cache poisoning (bsc#1261726).
• CVE-2026-32144: missing signature verification can lead to OCSP authorization bypass and information disclosure (bsc#1261734).

Other updates and bugfixes:

• jinterface: allow to build determenistic OtpErlang.jar (bsc#1262288).

This update for erlang fixes the following issues:

Security issues fixed:

• CVE-2026-21620: improper isolation and compartmentalization can lead to TFTP relative path traversal and remote arbitrary reads/writes (bsc#1258663).
• CVE-2026-23941: improper handling of duplicate Content-Length headers in Erlang OTP can lead to HTTP request smuggling (bsc#1259687).
• CVE-2026-23942: improper limitation of a pathname to a restricted directory in the SFTP server can lead to path traversal (bsc#1259681).
• CVE-2026-23943: improper handling of highly compressed data in Erlang OTP ssh can lead to denial of service (bsc#1259682).
• CVE-2026-28808: incorrect authorization can lead to unauthenticated access to protected CGI scripts (bsc#1261728).
• CVE-2026-28810: predictable DNS transaction IDs can lead to DNS cache poisoning (bsc#1261726).
• CVE-2026-32144: missing signature verification can lead to OCSP authorization bypass and information disclosure (bsc#1261734).

Other updates and bugfixes:

• jinterface: allow to build determenistic OtpErlang.jar (bsc#1262288).

This update for erlang26 fixes the following issues:

• CVE-2026-28810: predictable DNS transaction IDs can cause DNS cache poisoning (bsc#1261726).
• CVE-2026-42789: public_key application accepts non-CA certificates as intermediate issuers and this enables chain forgery (bsc#1266449).
• CVE-2026-42790: Name constraints and Subject CommonName fallback in TLS hostname verification allows for certificate forgery by MITM attacker (bsc#1266466).
• CVE-2026-42792: permanent epmd DoS via connection slot exhaustion due to improper handling of exceptional conditions (bsc#1272908).
• CVE-2026-47078: relative path traversal in zip:unzip/zip:extract via check_dir_level depth-counter bypass (bsc#1272909).
• CVE-2026-48855: SFTP READLINK response leaks absolute backend filesystem path when root is configured (bsc#1268139).
• CVE-2026-48856: httpc leaks Authorization headers to cross-origin redirect targets (bsc#1268141).
• CVE-2026-48858: server-side request forgery allows FTP bounce attacks and SSRF via an unvalidated PASV response IP address (bsc#1268142).
• CVE-2026-48860: ssl (inet_tls_dist module) allows unauthenticated bypass of the distribution-over-TLS LAN allowlist (bsc#1268146).
• CVE-2026-49759: unbounded stack buffer overflow in SCTP error cause parsing in inet_drv (bsc#1268163).
• CVE-2026-49760: stack buffer overflow in ei_s_print_term at very large integer (bsc#1268164).
• CVE-2026-53422: SFTP REALPATH path-existence oracle allows filesystem enumeration outside configured root (bsc#1270245).
• CVE-2026-54886: SSH SFTP server denial of service via extended channel data infinite loop (bsc#1270246).
• CVE-2026-54887: use of default cryptographic key allows predictable DTLS cookie computation during the startup window (bsc#1270247).
• CVE-2026-54891: plaintext injection towards (D)TLS client during handshake (bsc#1270250).
• CVE-2026-55737: heap pointer corruption via signed/unsigned mismatch in LARGE_TUPLE_EXTP decoding in erts external term format decoder (bsc#1272910).
• CVE-2026-55950: time-of-check time-of-use race condition allows an unauthenticated remote attacker to crash all active DTLS sessions on a listener (bsc#1270253).
• CVE-2026-55952: missing validation allows for DoS of the TLS-1.3 server when clients send a malformed ClientHello with mismatched PSK identity and binder list lengths (bsc#1270258).
• CVE-2026-55953: TLS 1.2 and DTLS clients accept unoffered anonymous cipher suites and allow for server authentication bypass (bsc#1272911).
• CVE-2026-58227: TLS/DTLS denial of service via unbounded recursion on cross-signed peer certificate chain (bsc#1272913).
• CVE-2026-59250: megaco flex scanner buffer overflow via oversized property parm name (bsc#1272914).
• CVE-2026-59251: denial of service via exponential certificate policy tree growth in path validation (bsc#1272915).

This update for erlang fixes the following issues:

• CVE-2026-28810: predictable DNS transaction IDs can cause DNS cache poisoning (bsc#1261726).
• CVE-2026-42789: public_key application accepts non-CA certificates as intermediate issuers and this enables chain forgery (bsc#1266449).
• CVE-2026-42790: Name constraints and Subject CommonName fallback in TLS hostname verification allows for certificate forgery by MITM attacker (bsc#1266466).
• CVE-2026-42792: permanent epmd DoS via connection slot exhaustion due to improper handling of exceptional conditions (bsc#1272908).
• CVE-2026-47078: relative path traversal in zip:unzip/zip:extract via check_dir_level depth-counter bypass (bsc#1272909).
• CVE-2026-48855: SFTP READLINK response leaks absolute backend filesystem path when root is configured (bsc#1268139).
• CVE-2026-48856: httpc leaks Authorization headers to cross-origin redirect targets (bsc#1268141).
• CVE-2026-48858: server-side request forgery allows FTP bounce attacks and SSRF via an unvalidated PASV response IP address (bsc#1268142).
• CVE-2026-49759: unbounded stack buffer overflow in SCTP error cause parsing in inet_drv (bsc#1268163).
• CVE-2026-49760: stack buffer overflow in ei_s_print_term at very large integer (bsc#1268164).
• CVE-2026-53422: SFTP REALPATH path-existence oracle allows filesystem enumeration outside configured root (bsc#1270245).
• CVE-2026-54886: SSH SFTP server denial of service via extended channel data infinite loop (bsc#1270246).
• CVE-2026-54887: use of default cryptographic key allows predictable DTLS cookie computation during the startup window (bsc#1270247).
• CVE-2026-54891: plaintext injection towards (D)TLS client during handshake (bsc#1270250).
• CVE-2026-55737: heap pointer corruption via signed/unsigned mismatch in LARGE_TUPLE_EXTP decoding in erts external term format decoder (bsc#1272910).
• CVE-2026-55952: missing validation allows for DoS of the TLS-1.3 server when clients send a malformed ClientHello with mismatched PSK identity and binder list lengths (bsc#1270258).
• CVE-2026-55953: TLS 1.2 and DTLS clients accept unoffered anonymous cipher suites and allow for server authentication bypass (bsc#1272911).
• CVE-2026-58227: TLS/DTLS denial of service via unbounded recursion on cross-signed peer certificate chain (bsc#1272913).
• CVE-2026-59250: megaco flex scanner buffer overflow via oversized property parm name (bsc#1272914).

Wander Nauta discovered that Erlang incorrectly handled absolute paths when extracting zip archives. An attacker could possibly use this issue to write arbitrary files outside of the intended directory. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2025-4748)

It was discovered that the Erlang SFTP server did not properly limit the size of packets. A remote attacker could possibly use this issue to cause Erlang to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 18.04 LTS. (CVE-2025-26618)

It was discovered that the Erlang SSH server did not properly limit the length of algorithm names in key exchange messages. A remote attacker could possibly use this issue to cause Erlang to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 18.04 LTS. (CVE-2025-30211)

It was discovered that the Erlang TFTP server incorrectly handled certain file paths. A remote attacker could possibly use this issue to access files outside of the intended directory. (CVE-2026-21620)

It was discovered that the Erlang SFTP server incorrectly validated paths against the configured root directory. An authenticated user could possibly use this issue to access files outside of the root directory. (CVE-2026-23942)

It was discovered that the Erlang SSH server enabled zlib compression by default and did not limit the size of decompressed data. A remote attacker could possibly use this issue to cause Erlang to use excessive resources, leading to a denial of service. (CVE-2026-23943)

It was discovered that the Erlang HTTP server incorrectly applied directory access controls to CGI scripts served via script aliases. A remote attacker could possibly use this issue to bypass authentication and access protected CGI scripts. (CVE-2026-28808)

It was discovered that the Erlang DNS resolver used predictable transaction IDs and did not randomize source ports. A remote attacker could possibly use this issue to perform DNS cache poisoning attacks. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-28810)

It was discovered that Erlang did not verify the signatures of designated OCSP responder certificates. A remote attacker could possibly use this issue to forge OCSP responses and bypass certificate revocation checks. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-32144)

It was discovered that the Erlang SFTP server incorrectly handled file attribute changes on open file handles. An authenticated user could possibly use this issue to modify the attributes of files outside of the root directory. (CVE-2026-32147)

It was discovered that Erlang incorrectly allowed non-CA certificates to act as intermediate certificate issuers. A remote attacker could possibly use this issue to forge certificate chains. (CVE-2026-42789)

It was discovered that Erlang incorrectly handled DNS name constraints during hostname verification. A remote attacker could possibly use this issue to bypass certificate validation. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-42790)

It was discovered that Erlang did not check the validity period of OCSP responder certificates. A remote attacker could possibly use this issue to forge OCSP responses using an expired responder certificate. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-42791)

It was discovered that Erlang incorrectly handled relative paths when extracting zip archives. An attacker could possibly use this issue to write arbitrary files outside of the intended directory. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-47078)

It was discovered that the Erlang SFTP server exposed absolute paths when reading symbolic links. An…