diff --git a/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.cpp b/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.cpp
new file mode 100644
index 00000000000..650e2c4062b
--- /dev/null
+++ b/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.cpp
@@ -0,0 +1,8 @@
+
+...
+char buf[256];
+X509_NAME_oneline(X509_get_subject_name(peer),buf,sizeof(buf)); // GOOD
+...
+char buf[256];
+X509_NAME_oneline(X509_get_subject_name(peer),buf,1024); // BAD
+...
diff --git a/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.qhelp b/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.qhelp
new file mode 100644
index 00000000000..c67d2c08895
--- /dev/null
+++ b/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.qhelp
@@ -0,0 +1,23 @@
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+<overview>
+<p>Using a size argument that is larger than the buffer size will result in an out-of-bounds memory access and possibly overflow. You need to limit the value of the length argument.</p>
+
+</overview>
+
+<example>
+<p>The following example shows the use of a function with and without an error in the size argument.</p>
+<sample src="BufferAccessWithIncorrectLengthValue.cpp" />
+
+</example>
+<references>
+
+<li>
+  CERT Coding Standard:
+  <a href="https://wiki.sei.cmu.edu/confluence/display/c/ARR38-C.+Guarantee+that+library+functions+do+not+form+invalid+pointers">ARR38-C. Guarantee that library functions do not form invalid pointers - SEI CERT C Coding Standard - Confluence</a>.
+</li>
+
+</references>
+</qhelp>
diff --git a/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.ql b/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.ql
new file mode 100644
index 00000000000..0683e81ddd3
--- /dev/null
+++ b/cpp/ql/src/experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.ql
@@ -0,0 +1,76 @@
+/**
+ * @name Buffer access with incorrect length value
+ * @description Incorrect use of the length argument in some functions will result in out-of-memory accesses.
+ * @kind problem
+ * @id cpp/buffer-access-with-incorrect-length-value
+ * @problem.severity warning
+ * @precision medium
+ * @tags correctness
+ *       security
+ *       experimental
+ *       external/cwe/cwe-805
+ */
+
+import cpp
+
+/** Holds for a function `f`, which has an argument at index `bpos` that points to a buffer and an argument at index `spos` that points to a size. */
+predicate numberArgument(Function f, int bpos, int spos) {
+  f.hasGlobalOrStdName([
+      "X509_NAME_oneline", "SSL_CIPHER_description", "SSL_get_shared_ciphers",
+      "SSL_export_keying_material_early", "SSL_export_keying_material", "SSL_set_alpn_protos",
+      "SSL_CTX_set_alpn_protos", "SSL_read", "SSL_read_ex", "SSL_read_early_data",
+      "SSL_bytes_to_cipher_list", "SSL_write", "SSL_SESSION_set1_master_key",
+      "SSL_CTX_set_session_id_context", "BIO_gets", "BIO_read", "BIO_read_ex", "BIO_write",
+      "BIO_write_ex", "BIO_ctrl", "BN_bn2binpad", "BN_signed_bn2bin", "BN_signed_bn2lebin",
+      "EVP_PKEY_get_default_digest_name", "EVP_DigestUpdate", "EVP_PKEY_CTX_set1_tls1_prf_secret",
+      "EVP_KDF_derive", "EVP_CIPHER_CTX_get_updated_iv", "EVP_PKEY_get_group_name", "EVP_MAC_init",
+      "write", "read", "send", "sendto", "recv", "recvfrom", "strerror_r"
+    ]) and
+  bpos = 1 and
+  spos = 2
+  or
+  f.hasGlobalOrStdName(["X509_NAME_get_text_by_NID", "EVP_PKEY_get_utf8_string_param"]) and
+  bpos = 2 and
+  spos = 3
+  or
+  f.hasGlobalOrStdName([
+      "BIO_snprintf", "BN_signed_lebin2bn", "BIO_new_mem_buf", "BN_lebin2bn", "BN_bin2bn",
+      "EVP_read_pw_string", "EVP_read_pw_string", "strftime", "strnlen", "fgets", "snprintf",
+      "vsnprintf"
+    ]) and
+  bpos = 0 and
+  spos = 1
+  or
+  f.hasGlobalOrStdName(["AES_ige_encrypt", "memchr"]) and bpos = 0 and spos = 2
+  or
+  f.hasGlobalOrStdName("EVP_MAC_final") and bpos = 1 and spos = 3
+  or
+  f.hasGlobalOrStdName("OBJ_obj2txt") and bpos = 2 and spos = 1
+  or
+  f.hasGlobalOrStdName("EVP_CIPHER_CTX_ctrl") and bpos = 3 and spos = 2
+  or
+  f.hasGlobalOrStdName(["EVP_PKEY_get_octet_string_param", "getnameinfo"]) and bpos = 2 and spos = 3
+  or
+  f.hasGlobalOrStdName([
+      "EVP_DecryptUpdate", "EVP_EncryptUpdate", "EVP_PKEY_encrypt", "EVP_PKEY_sign",
+      "EVP_CipherUpdate"
+    ]) and
+  bpos = 3 and
+  spos = 4
+  or
+  f.hasGlobalOrStdName("getnameinfo") and bpos = 4 and spos = 5
+}
+
+from FunctionCall fc
+where
+  exists(ArrayType array, int bufArgPos, int sizeArgPos |
+    numberArgument(fc.getTarget(), bufArgPos, sizeArgPos) and
+    fc.getArgument(pragma[only_bind_into](sizeArgPos)).getValue().toInt() > array.getByteSize() and
+    fc.getArgument(pragma[only_bind_into](bufArgPos))
+        .(VariableAccess)
+        .getTarget()
+        .getADeclarationEntry()
+        .getType() = array
+  )
+select fc,
+  "Access beyond the bounds of the allocated memory is possible, the size argument used is greater than the size of the buffer."
diff --git a/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/BufferAccessWithIncorrectLengthValue.expected b/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/BufferAccessWithIncorrectLengthValue.expected
new file mode 100644
index 00000000000..d0d9fbad694
--- /dev/null
+++ b/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/BufferAccessWithIncorrectLengthValue.expected
@@ -0,0 +1 @@
+| test.cpp:27:5:27:21 | call to X509_NAME_oneline | Access beyond the bounds of the allocated memory is possible, the size argument used is greater than the size of the buffer. |
diff --git a/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/BufferAccessWithIncorrectLengthValue.qlref b/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/BufferAccessWithIncorrectLengthValue.qlref
new file mode 100644
index 00000000000..6cbb5527211
--- /dev/null
+++ b/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/BufferAccessWithIncorrectLengthValue.qlref
@@ -0,0 +1 @@
+experimental/Security/CWE/CWE-805/BufferAccessWithIncorrectLengthValue.ql
diff --git a/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/test.cpp b/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/test.cpp
new file mode 100644
index 00000000000..26c33abab65
--- /dev/null
+++ b/cpp/ql/test/experimental/query-tests/Security/CWE/CWE-805/semmle/tests/test.cpp
@@ -0,0 +1,31 @@
+struct X509_NAME {};
+struct SSL {};
+struct X509 {};
+
+char * X509_NAME_oneline(X509_NAME *a,char *buf,int size);
+X509 *SSL_get_peer_certificate(const SSL *ssl);
+X509_NAME *X509_get_subject_name(const X509 *x);
+char *strcasestr(char *a, char *b);
+
+bool goodTest1(SSL *ssl,char *text)
+{
+  X509 *peer;
+  char buf[256];
+  if( peer = SSL_get_peer_certificate(ssl))
+  {
+    X509_NAME_oneline(X509_get_subject_name(peer),buf,sizeof(buf)); // GOOD
+    if((char*)strcasestr(buf,text)) return true;
+  }
+  return false;
+}
+bool badTest1(SSL *ssl,char *text)
+{
+  X509 *peer;
+  char buf[256];
+  if( peer = SSL_get_peer_certificate(ssl))
+  {
+    X509_NAME_oneline(X509_get_subject_name(peer),buf,1024); // BAD
+    if((char*)strcasestr(buf,text)) return true;
+  }
+  return false;
+}